;--------------------------------------------------------------------------
;  __strreverse.s
;
;  Copyright (C) 2020, Sergey Belyashov
;
;  This library is free software; you can redistribute it and/or modify it
;  under the terms of the GNU General Public License as published by the
;  Free Software Foundation; either version 2, or (at your option) any
;  later version.
;
;  This library is distributed in the hope that it will be useful,
;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;  GNU General Public License for more details.
;
;  You should have received a copy of the GNU General Public License 
;  along with this library; see the file COPYING. If not, write to the
;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
;   MA 02110-1301, USA.
;
;  As a special exception, if you link this library with other files,
;  some of which are compiled with SDCC, to produce an executable,
;  this library does not by itself cause the resulting executable to
;  be covered by the GNU General Public License. This exception does
;  not however invalidate any other reasons why the executable file
;   might be covered by the GNU General Public License.
;--------------------------------------------------------------------------

        .area   _CODE

        .globl ___strreverse
        .globl ___strreverse_reg
;
;char * __reverse(char *beg, char *end);
;
___strreverse::
        pop     bc
        pop     de
        pop     hl
        push    hl
        push    de
        push    bc

;in: HL - pointer to end of string (null symbol), DE - pointer to start of string
;
___strreverse_reg::
        push    de
        jr      110$
100$:
        add     hl, de
        ld      a, (de)
        ld      c, (hl)
        ld      (hl), a
        ld      a, c
        ld      (de), a
        inc     de
110$:
        dec     hl
        or      a, a
        sbc     hl, de
        jr      NC, 100$
        pop     hl
        ret
